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首页> 外文期刊>Phase Transitions >Phase stability, mechanical and thermodynamic properties of orthorhombic and trigonal MgSiN2: an ab initio study
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Phase stability, mechanical and thermodynamic properties of orthorhombic and trigonal MgSiN2: an ab initio study

机译：正交和三角形MgSiN2的相稳定性，力学和热力学性质：从头算研究

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摘要

Structural stability and mechanical and thermodynamic properties of the orthorhombic and trigonal MgSiN2 polymorphs (or-MgSiN2 and tr-MgSiN2) were investigated through density functional theory and quasi-harmonic Debye model (QHDM). Our calculations show that or-MgSiN2 is energetically the stable polymorph at low pressure, in agreement with previous experimental and theoretical study. Under pressure, a crystallographic transition from the orthorhombic structure to the trigonal one occurs around 25, 17.45 and 19.05 GPa as obtained from the generalized gradient approximation of Perdew-Wang (GGA-PW91), the generalized gradient approximation parameterized recently by Perdew et al (GGA-PBEsol) and the local density approximation developed by Ceperley and Alder and parameterized by Perdew and Zunger (LDA-CAPZ), respectively. Single-crystalline and polycrystalline elastic constants and related properties, namely Vickers hardness, acoustic Gruneisen parameter, minimum thermal conductivity, isotropic sound velocities and Debye temperature, were numerically estimated for both or-MgSiN2 and tr-MgSiN2. We have showed that the hardness of tr-MgSiN2 is comparable to that of the harder materials like c-BN and B6O. Temperature and pressure dependencies of volume, bulk modulus, thermal expansion, Gruneisen parameter, heat capacities and Debye temperature were investigated using QHDM.
机译：通过密度泛函理论和准谐波德拜模型（QHDM）研究了正交和三角形MgSiN2多晶型物（或-MgSiN2和tr-MgSiN2）的结构稳定性以及力学和热力学性质。我们的计算表明，与以前的实验和理论研究相一致，or-MgSiN2在低压下在能量上是稳定的多晶型物。在压力下，从Perdew-Wang（GGA-PW91）的广义梯度近似获得的，从正交结构到三角晶体的晶体学转变发生在25、17.45和19.05 GPa处，这是Perdew等人最近设定的广义梯度近似（分别由Ceperley和Alder开发并由Perdew和Zunger（LDA-CAPZ）参数化。对or-MgSiN2和tr-MgSiN2均进行了数字估算，得出了单晶和多晶弹性常数及其相关特性，即维氏硬度，声学Gruneisen参数，最小导热率，各向同性声速和德拜温度。我们已经证明，tr-MgSiN2的硬度与c-BN和B6O等较硬材料的硬度相当。使用QHDM研究了体积，体积模量，热膨胀，Gruneisen参数，热容量和德拜温度对温度和压力的依赖性。

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